Blue LED-Associated Morphological Changes and Gene Expression Responses in Trichoderma harzianum

As LEDs are increasingly used in mushroom production, understanding the blue-light response characteristics of the pathogenic fungus Trichoderma harzianum is important for mushroom cultivation management. In this study, T. harzianum was cultured under blue LED conditions (460 nm), with darkness as the control, and its growth, morphology, and transcriptomic responses were compared. Blue LED exposure reduced colony diameter by 21.6% and 25.2% on days 1 and 2 of cultivation, respectively, and induced sporulation on day 3. RNA-seq Trinity gene-level features were quantified, and 23,086 and 34,839 genes showed higher and lower expression under blue LED illumination, respectively. Gene Ontology (GO) analysis of candidates selected using the criteria TPM ≥ 15 and |log2FC| ≥ 1 showed that the candidates with increased expression blue LED illumination were associated with transport and xenobiotic transport, whereas the candidates with decreased expression were associated with filamentous growth, cell wall polysaccharide biosynthetic process, and UDP-glucosyltransferase activity. Among the highly responsive candidates selected using the criteria TPM ≥ 15 and |log2FC| ≥ 3, carbohydrate-active enzyme (CA-Zyme)-related genes were identified, including glycosyltransferase family (GT) 8, GT35, glycoside hydrolase family (GH) 16, GH18, GH76, and multicopper oxidase. In contrast, the candidates with decreased expression included GT2, GT20, GT35, carbohydrate esterase family 5, and GMC oxidoreductase. RT-qPCR analysis of the selected candidate genes supported the RNA-seq-based expression trends. In addition, in the RNA-seq dataset, the expression levels of the blue light response-related genes BLR-1, BLR-2, and ENV1 increased by 2.8-, 1.9-, and 4.2-fold, respectively. These findings provide phenotypic and molecular candidates for future functional studies of the blue-light response in T. harzianum.